The present invention relates to a robot compliance device and, more particularly, to a robot compliance device that has a simple structure and that can avoid undesired angular misalignment during operation.
Robots are widely utilized in many industries for various purposes. In one application, robots are utilized to assemble a first part such as a precise shaft, a pin, or a bearing into a hole of a second part. Many compliance devices have been developed to compensate misalignment between axes of the first and second parts due to machine inaccuracy, vibration, or tolerance during assembly. A typical compliance device generally includes an upper plate attached to a bracket of a robot, a lower plate carrying the first part, and a plurality of elastic bodies between the upper and lower plates. When the first part is subjected to a reactive force resulting from the misalignment between the axes of the first and second parts, the elastic bodies are compressed and/or twisted and translate in a direction perpendicular to the axis of the second part to bring the axis of the first part toward the axis of the second part. However, the elastic bodies may bend in an undesired manner as a result of a large insertion force required in assembly. As a result, assembly can not be performed properly, since the first part held by the lower plate is liable to be inclined due to undesired angular misalignment between the axes resulting from compression of the elastic bodies along the axis of the first part. In an approach to solve the problem resulting from the large insertion force, a plurality of rigid limiters are mounted between the lower plate and the bracket of the robot and extended through the upper plate. The limiters come in contact with the bracket after the lower plate has been moved toward the upper plate through a predetermined travel, limiting further travel of the lower plate to prevent undesired bending of and/or damage to the elastic bodies. However, undesired angular misalignment still exists during assembly, for the elastic bodies are still compressed along the axis of the first part. Aside from the above problems, the above compliance devices suffer from the common disadvantages including but not limited to being expensive, having complicated structures and having limited applications such as limited working force ranges.
Thus, a need exists for a robot compliance device that has a simple structure and that can be easily modified according to needs while providing desired spherical compliance.